Your DEXA report says T-score -2.3. Now what? Most patients leave their DEXA appointment with a number but no framework for what it means day-to-day. Here's how to read your results.
The T-score compares your bone mineral density (BMD) to a reference database of young healthy adults at peak bone mass — typically women aged 20–29 from the NHANES III database. Each 1.0 unit represents one standard deviation below that peak. A T-score of -2.3 means your bone density is 2.3 standard deviations below the average young healthy adult.
The WHO classification system, used worldwide including in Canada, defines three categories:
| T-Score Range | Classification |
|---|---|
| ≥ −1.0 | Normal bone density |
| −1.0 to −2.5 | Osteopenia (low bone mass) |
| ≤ −2.5 | Osteoporosis |
| ≤ −2.5 + fragility fracture | Severe (established) osteoporosis |
The cutoff of -2.5 was chosen by the WHO in 1994 based on the prevalence of fractures in postmenopausal women. It was not designed as a universal treatment threshold — that decision involves more than just the number on the report.
The Z-score compares your BMD to age- and sex-matched peers. A Z-score of -2.0 means you're in the bottom 2.5% for your age group — your bone density is unusually low relative to people your age.
Z-score matters most for younger patients — pre-menopausal women and men under 50. For these groups, comparing BMD to young adults (the T-score reference) is less clinically meaningful, since some age-related bone loss hasn't yet occurred. Osteoporosis Canada and the International Society for Clinical Densitometry (ISCD) recommend using Z-score as the primary interpretation for premenopausal women and men under 50.
A Z-score ≤ -2.0 at any age warrants investigation for secondary causes of bone loss. Common secondary causes include: prolonged glucocorticoid use, primary hyperparathyroidism, celiac disease or other malabsorption syndromes, vitamin D deficiency, hypogonadism, and hyperthyroidism. If your Z-score is this low, the bone loss may not be primarily due to aging or menopause.
Standard DEXA measures two sites: the lumbar spine (vertebrae L1–L4) and the hip (femoral neck and total hip). These sites can produce very different results — it's entirely possible to have a T-score of -3.0 at the lumbar spine and -1.5 at the hip in the same person.
The rule: the lowest T-score across both sites drives diagnosis and treatment decisions. If your spine is -2.8 and your hip is -1.7, your diagnosis is based on the -2.8.
Discordance between sites is common. Spine results can be artificially elevated (appearing falsely normal) by degenerative joint disease, osteophytes, aortic calcification, or prior vertebral fractures — all of which add density to the scan without representing actual bone strength. If you're over 60 with spine arthritis, your spine T-score may underestimate your actual fracture risk.
TBS is a texture analysis applied to the lumbar spine DEXA image that estimates bone microarchitecture — essentially, the three-dimensional structure of the bone's internal scaffolding. It is distinct from BMD. Two people can have identical T-scores but very different TBS values, reflecting different fracture risks.
TBS is classified as:
The clinical value of TBS is highest in situations where BMD may not fully reflect fracture risk. Long-term glucocorticoid (prednisone) use, for example, impairs bone quality through mechanisms that aren't fully captured by BMD — TBS picks up this degradation. Similarly, TBS adds independent fracture risk information in patients with type 2 diabetes, where BMD can be misleadingly normal or even elevated despite higher fracture rates.
TBS can also be fed into the FRAX calculator (described below) to adjust fracture probability, a feature now included in the Canadian FRAX tool.
FRAX (Fracture Risk Assessment Tool) is a WHO-developed algorithm that calculates your 10-year probability of a major osteoporotic fracture (hip, spine, forearm, or shoulder) and your 10-year probability of a hip fracture specifically. The Canadian FRAX model is available at sheffield.ac.uk/FRAX — select Canada as the country.
FRAX inputs your femoral neck T-score (not spine) plus 12 clinical risk factors:
The output is a percentage. A result of 22% major osteoporotic fracture risk means roughly 22 out of 100 people with your profile will fracture in the next 10 years. Your physician uses Osteoporosis Canada's treatment thresholds — typically a 10-year major fracture probability ≥ 20% or hip fracture probability ≥ 3% — to guide medication decisions.
This is where many patients are surprised. Your T-score may be -1.8 (osteopenia), but treatment could still be indicated based on your overall FRAX profile. Several factors increase fracture probability substantially regardless of BMD:
Osteoporosis Canada's guidance on DEXA frequency:
Provincial coverage varies. In Ontario, DEXA is covered by OHIP for patients meeting specific criteria — age over 50 with a fragility fracture, anyone over 65, those on long-term glucocorticoids, and other defined risk groups. Coverage in BC, Alberta, and Quebec has its own criteria — worth confirming with your provincial health plan before assuming the follow-up is covered.
When your physician says your DEXA is "stable," that requires context. Every DEXA machine has a measurement imprecision — a number called the Least Significant Change (LSC). At most centres, the LSC for lumbar spine BMD is approximately 3–5%. A change smaller than the LSC is statistically indistinguishable from measurement noise.
This matters when you're comparing results over time, especially across different machines or centres. A drop from -2.1 to -2.3 may look meaningful on paper, but if the LSC at your centre is 4%, that change is within error. Conversely, a drop from -2.0 to -2.5 — a 0.5 SD change — likely reflects true bone loss.
Ask your DEXA technologist or your physician: "What is the LSC for this centre?" before drawing conclusions from year-over-year comparisons. Comparing results from two different machines is particularly unreliable.